Ratcheted fuel cap

ABSTRACT

A fuel tank cap that is engageable with a neck of a fuel tank. The fuel tank cap includes a cap shell that has a cover portion and a substantially cylindrical wall extending from the cover portion to define a substantially cylindrical chamber. An arm extends from the cover portion toward the fuel tank. An inner shell is at least partially disposed within the cylindrical chamber. The inner shell includes an engagement portion that is engageable with the neck and a protrusion that is engageable with the arm to selectively couple the cap shell and the inner shell for rotation in unison.

BACKGROUND

The present invention relates to a fuel tank cap, and particularly to a fuel tank cap that inhibits overtightening and indicates proper tightening.

Internal combustion engines are often used to power small equipment such as lawnmowers, tillers, snow throwers, pressure washers, generators, and the like. Typically, these engines include a fuel system that supplies fuel for combustion. The fuel system includes a tank, in which fuel is stored for use and a cap that can be removed to add fuel to the tank. The fuel tank cap is typically threaded on the tank or on a fill spout attached to the tank.

Generally, small engines include a fuel tank cap that includes a gasket or resilient component that seals against the tank fill spout. The gasket is designed to provide a seal when tightened to a predetermined torque. However, some users tend to overtighten or undertighten the fuel tank cap. When the cap is overtightened, the gasket becomes crushed and can become damaged. The damage can reduce the effectiveness of the gasket, thus resulting in excess fuel vapor leakage, increased evaporative emissions, and spillage during operation. If the cap is undertightened, the gasket cannot provide a proper seal, thus resulting in excess fuel vapor leakage, increased evaporative emissions, and spillage during operation.

SUMMARY

The invention provides a fuel tank cap that is engageable with a neck of a fuel tank. The fuel tank includes a fuel chamber that is adapted to contain fuel. The fuel tank cap includes a cap shell that has a cover portion and a substantially cylindrical wall extending from the cover portion to define a substantially cylindrical chamber. An arm extends from the cover portion toward the fuel chamber of the fuel tank when the cap is installed on the fuel tank. The arm defines a longitudinal axis that is substantially orthogonal to the cover portion. An inner shell is at least partially disposed within the cylindrical chamber. The inner shell includes an engagement portion that is engageable with the neck and a protrusion that is engageable with the arm to selectively couple the cap shell and the inner shell for rotation in unison.

The invention also provides a fuel tank cap engageable with a neck that defines a neck axis. The fuel tank cap includes an inner shell that is rotatable relative to the neck to move between an engaged position and a disengaged position. A cap shell includes an arm that defines an arm axis. A protrusion extends from the inner shell. The protrusion cooperates with the arm to couple the inner shell and the cap shell for rotation in unison from the disengaged position to the engaged position. The protrusion displaces the arm such that the cap shell rotates independent of the inner shell when rotated beyond the engaged position. The protrusion is engaged with the arm to couple the inner shell and the cap shell for rotation in unison from the engaged position to the disengaged position.

The invention also provides a fuel cap that is engageable with a neck of a fuel tank that defines a neck axis. The fuel tank also includes a fuel chamber adapted to contain fuel. The fuel cap includes a cap shell that has a cover portion that is substantially normal to the neck axis and a substantially cylindrical wall that extends from the cover portion to define a substantially cylindrical chamber. An arm extends from the cover portion toward the fuel chamber of the fuel tank. An inner shell is at least partially disposed within the cylindrical chamber and is engageable with the neck. The inner shell is rotatable relative to the neck to move between a disengaged position and an engaged position. A protrusion has a first side and a second side. The first side is engageable with the arm to couple the cap shell and inner shell for rotation from the engaged position to the disengaged position. The second side is engageable with the arm to couple the cap shell and inner shell for rotation from the disengaged position to the engaged position when a rotational torque is below an engaged value. The second side is operable to displace the arm such that the cap shell rotates independent of the inner shell when the rotational torque exceeds the engaged value.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figures in which:

FIG. 1 is a perspective view of an engine including a fuel tank cap;

FIG. 2 is a perspective view of the fuel cap and fill neck of FIG. 1;

FIG. 3 is an exploded perspective view of the fuel tank cap of FIG. 1;

FIG. 4 is a section view of the fuel cap of FIG. 2 taken along line 4-4 of FIG. 2;

FIG. 5 is an exploded view of a portion of the fuel tank cap of FIG. 2;

FIG. 6 is a bottom view of a portion of the fuel tank cap of FIG. 2 in a loosening position; and

FIG. 7 is a bottom view of a portion of the fuel tank cap of FIG. 2 in a tightening position.

DETAILED DESCRIPTION

With reference to FIG. 1, an engine 10 including a fuel tank 15 with a fuel tank cap 20 is illustrated. The fuel tank 15 includes a fill neck 25 (shown in FIG. 2) that extends from the tank 15 and provides an opening to the tank fuel chamber that is adapted to contain fuel. Generally, the fill neck 25 includes external threads 30 and the cap 20 includes internal threads 35 (shown in FIG. 3) that allow the cap 20 to threadably engage the fill neck 25.

As shown in FIG. 3, the fuel cap 20 includes a cap shell 40 or outer shell that includes a cover portion 45 and a substantially cylindrical wall 50 that extends away from the cover portion 45 to define a cylindrical chamber 55. In most constructions, the cylindrical wall 50 is orthogonal to the cover portion 45 and substantially parallel to a neck axis 60 defined by the fill neck 25. However, other angles could also be employed if desired. A plurality of lobes 65 extend radially outward from the cylindrical wall 50 to form a more ergonomic grip surface. The construction illustrated herein includes five lobes 65 that each define a substantially hollow lobe space 70 and that are spaced around the cylindrical wall 50. The five lobes 65 illustrated in FIG. 2 are spaced approximately seventy-two degrees apart from one another. Of course other constructions may include fewer lobes 65 or more lobes 65. In addition, the lobes 65 could be spaced apart by non-equal angles to further improve the ergonomic shape of the cap shell 40 if desired.

With continued reference to FIG. 3, the cap shell 40 includes a plurality of arms 75 that extend from the cover portion 45 toward the fuel tank 15 and define longitudinal axes 80 that are preferably substantially parallel to the cylindrical wall 50. The arms 75 are supported in a cantilever fashion such that they are only supported at one end. As illustrated in FIGS. 6 and 7, some constructions include arms 75 that are supported substantially in a cantilever fashion but that include a thin wall 76 extending along at least one side of the arm. The thin wall 76 inhibits twisting and non-radial deflection of the arm 75 but does not significantly change the stiffness of the arms 75 in the radial direction. In other constructions, the arms 75 extend from the cover portion 45 but are not parallel to the cylindrical walls 50. In addition, constructions that support the arms 75 in a manner other than a cantilever fashion are also contemplated by the invention.

Each arm 75 is disposed near one of the lobe spaces 70 such that a radially outward force applied to the arm 75 will deflect the arm 75 into the lobe space 70. The cap shell 40 also includes a circumferential groove 85 and a clearance space 90 that extend around the interior of the cylindrical wall 50.

In addition to the cap shell 40, the fuel tank cap 20 includes an inner shell 95 and a gasket 100. The inner shell 95, best illustrated in FIG. 5, includes a cylindrical portion 105 that defines an outer surface 110 and an inner surface 115. The outer surface 110 includes a circumferential bead 120 that surrounds the outer surface 110 and is sized to engage the groove 85 of the cap shell 40. Once engaged, the position of the inner shell 95 relative to the cap shell 40 is fixed along the neck axis 60. However, the inner shell 95 remains free to rotate about the neck axis 60 relative to the cap shell 40. It should also be noted that while the illustrated construction includes a circumferential bead 120 on the inner shell 95 and a corresponding groove 85 in the cap shell 40, the location of the bead 120 and groove 85 could be reversed. In addition, there is no requirement that the bead 120 and groove 85 extend completely around the inner shell 95 and the cap shell 40.

The outer surface 110 also includes a plurality of protrusions 125 that extend radially outward from the outer surface 110. In most constructions, there is one protrusion 125 for each arm 75. Thus, in the illustrated constructions, there are five protrusions 125 extending from the outer surface 110. Of course, other constructions may employ fewer protrusions 125 than arms 75, or more protrusions 125 than arms 75 if desired. For example, one construction may include two protrusions 125 for each arm 75.

The inner surface 115 of the inner shell 95 includes threads 35 that correspond with the threads 30 of the fill neck 25. Thus, when the cap 20 is installed on the fuel tank 15, the inner shell 95 engages the fill neck 25 and is rotated relative to the fill neck 25 to loosen or tighten the cap 20.

As shown in FIG. 3, a second cylindrical wall 130 extends from the inner shell 95 and defines a chamber 135 that is sized to receive an additive container 140. The additive container includes a fuel additive such as a rust inhibitor, an anti-oxidant, and/or a metal deactivator and is described in greater detail in U.S. patent application Ser. Nos. 10/209,687 and 10/465,499 both of which are fully incorporated herein by reference. The chamber 135 includes an engagement surface 145 (shown in FIG. 4) that engages the additive container 140 and holds the container 140 in place, while still allowing for the removal and replacement of the container 140. A puncture device 150 is formed within the chamber 135 and is positioned to punch a hole in the additive container 140 to provide a vent that improves additive container function. While the construction of FIG. 3 includes an additive container 140, the container 140 is not necessary for the invention to function.

The inner shell 95 includes a substantially planar flange 155 that extends around the end of the cylindrical portion 105 and cooperates with the cap shell 40 to trap a tether 160 as shown in FIG. 4. The tether 160, best illustrated in FIG. 3, includes a first cylindrical lobe 165 that is sandwiched between the flange 155 and the cap shell 40, and a second cylindrical lobe 170 that attaches to the fuel tank 15 or the engine 10. The tether 160 maintains an attachment between the fuel tank 15 or engine 10 and the fuel tank cap 20 even when the cap 20 is removed from the fill neck 25. This attachment reduces the likelihood that the user would lose the cap 20. Of course not all fuel caps 20 employ a tether 160 and its use is not critical to the function of the invention.

The gasket 100 (sometimes referred to as a liner or seal) fits within the inner shell 95 and cooperates with the fill neck 25 to form a seal. As illustrated in FIG. 3, the liner is a generally flat resilient component that can deform or compress slightly as the cap 20 is tightened onto the fill neck 25. The gasket 100 can be coupled to the inner shell 95 using any suitable means including adhesive, welding, threading, keys, cams, fasteners, and the like. Generally, the gasket 100 is formed from a softer material than the inner shell 95. This allows the gasket 100 to compress as it makes contact with the fill neck 25 to form a better seal. As the gasket 100 compresses, increased torque is required to continue turning the cap 20.

In another construction, the gasket 100 cooperates with the inner surface of the inner shell 95 to define a tapered neck-receiving space. Because the neck-receiving space is tapered, the torque required to tighten the fuel tank cap 20 is not constant. Rather, the torque that must be applied to tighten the cap 20 continues to increase as the cap 20 is tightened and the fill neck 25 extends into the more narrow portions of the neck-receiving space. The fill neck 25 compresses the gasket 100 as it moves into the neck-receiving space to establish a seal between the cap 20 and the fill neck 25.

In another construction, the gasket 100 and inner shell 95 are formed together as a single component. This construction has the advantages of reducing the number of components and the complexity of the assembly. However, it is not possible to use different materials in this construction. As such, the seal achievable with this construction may not be suitable in all applications.

With reference to FIGS. 6 and 7, the details of the arms 75 and the protrusions 125 will be described. While FIGS. 6 and 7 illustrate a single arm 75 and protrusion 125, each arm 75 and protrusion 125 are substantially the same as those illustrated. As such, only the one arm 75 and protrusion 125 will be described. In addition, FIGS. 6 and 7 are bottom views of the fuel tank cap 20. As such, a movement of the components in a clockwise direction 180 in FIGS. 6 and 7 would be the result of a counterclockwise rotation of the fuel tank cap 20 relative to the fill neck 25 as perceived by a user. Thus, a movement of the components in the clockwise direction 180 (from the bottom view) in FIGS. 6 and 7 would result in the fuel tank cap 20 loosening from, or being removed from the fill neck 25 (assuming standard right-hand threads are employed). A counterclockwise movement 185 (from the bottom view) of the components results in the tightening of the fuel tank cap 20 onto the fill neck 25.

The arm 75 includes a first angled surface 190 on the clockwise side (from the bottom view) and a second angled surface 195 on the counterclockwise side (from the bottom view). While both surfaces 190, 195 could be angled such that they are parallel, the second surface 195 is angled more acutely than the first surface 190. The protrusion 125 includes a planar surface 200 and an arcuate surface 205. The planar surface 200 is disposed on the counterclockwise side (from the bottom view) of the protrusion 125 and the arcuate surface 205 is disposed on the clockwise side (from the bottom view). The planar surface 200 is angled to substantially match the angle of the first angled surface 190.

With reference to FIG. 7, the cap shell 40 is shown as it is being rotated in the counterclockwise direction 185 (from the bottom view). The protrusions 125 pass through the clearance space 90 formed in the cap shell 40 such that the arcuate surface 205 engages the second angled surface 195 of the arm 75. The arcuate surface 205 and second angled surface 195 are oriented such that a force that tends to displace the arm 75 radially outward is established. However, during the initial tightening of the cap 20, the friction between the arcuate surface 205 and the arm 75 and the stiffness of the arm (i.e., the arm's resistance to bending) are sufficient to allow rotation of both the inner shell 95 and the cap shell 40 in unison. As the fill neck 25 begins to extend into the neck-receiving space, additional torque is required to tighten the cap 20. The additional torque generates a larger force between the arcuate surface 205 and the second angled surface 195. Eventually, the force generated by the torque is great enough to displace the arm 75 and allow the protrusion 125 to pass. At this point, the cap 20 cannot be tightened more, as the cap shell 40 rotates independent of the inner shell 95.

In operation, the fuel tank cap 20 is positioned on the fill neck 25 and rotated to begin tightening the cap 20. The cap shell 40 rotates about the neck axis 60 independent of the inner shell 95 until the arcuate surfaces 205 of the protrusions 125 engage the second angled surfaces 195, as illustrated in FIG. 7. The cap shell 40 and the inner shell 95 then rotate together in unison until the fill neck 125 begins to extend into the cap 20 and compress the gasket 100. As the fill neck 125 compresses the gasket 100, the torque required to continue turning the cap shell 40 increases. As the torque increases, additional force is required to maintain the connection between the cap shell 40 and the inner shell 95. To generate the additional friction, the arcuate surfaces 205 rotate further relative to the second angled surfaces 195. The additional rotation of the arcuate surfaces 205 displaces the arms 75. Thus, the arms 75 exert an increased reaction force against the arcuate surfaces 205. The increased reaction forces produce an increase in the normal forces and thus, the frictional forces between the arcuate surfaces 205 and the second angled surfaces 195. At a predetermined torque value, the friction between the arcuate surfaces 205 and the second angled surfaces 195 is insufficient to maintain their engagement and the arms 75 are pushed into the lobe spaces 70. Any efforts to further tighten the fuel tank cap 20 produce free rotation of the cap shell 40 without any rotation of the inner shell 95. In addition, further rotation will produce a “clicking” sound that is typically audible to the user and a tactile sensation, both of which indicate that the cap 20 is properly installed and tightened. Thus, with a proper choice of the angle of the second angled surfaces 195 and the shape of the arcuate surfaces 205, the inner shell 95 can be rotated to a predetermined torque repeatably, thus improving the likelihood of a properly seated fuel tank cap 20 each time it is placed on the fill neck 25.

As shown in FIG. 6, with the cap shell 40 rotated in the clockwise direction 180 (loosening) the planar surface 200 engages the first angled surface 190. The angled surface 140 and planar surface 200 are arranged such that the force generated between the contacting surfaces 190, 200 tends to push the arm 75 radially inward, thus maintaining the arm 75 and protrusion 125 in a locked arrangement such that the inner shell 95 and cap shell 40 rotate in unison regardless of the torque applied.

Thus, to remove the cap 20, the cap shell 40 is rotated in the clockwise direction 180 (as shown in FIG. 6). The cap shell 40 rotates independent of the inner shell 95 until the planar surface 200 engages the first angled surface 190. Because the planar surface 200 and the first angled surface 190 are arranged to maintain the position of the arm 75 and not displace the arm 75 into the lobe space 70, the inner shell 95 and the cap shell 40 remain engaged with one another regardless of the torque applied to the cap shell 40. Thus, rotation of the cap shell 40 also rotates the inner shell 95 to allow for the removal of the cap 20.

The cap arrangement described herein increases the likelihood that a proper seal between the cap 20 and the fill neck 25 is established each time the cap 20 is installed. In addition, the cap 20 provides both audible and tactile feedback to the user that indicates that the cap 20 has been properly tightened. Furthermore, the arrangement of the arms 75 within the cap 20 (and displaceable into the lobe spaces 75), allows for a cap 20 that has a reduced height when compared to other caps. The reduced height is particularly advantageous when the engine is used with equipment that includes an engine cover such as riding lawn mowers, snow throwers, and the like. The reduced height of the cap allows for a closer fit between the cover and the engine. In addition, tall caps can be unsightly and thus undesirable, while wide caps are generally more visually appealing and do not require additional space as they are typically disposed on top of a wide fuel tank.

Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims. 

1. A fuel tank cap engageable with a neck of a fuel tank, the fuel tank having a fuel chamber adapted to contain fuel, the fuel tank cap comprising: a cap shell including a cover portion and a substantially cylindrical wall extending from the cover portion to at least partially define a substantially cylindrical chamber; an arm extending from the cover portion toward the fuel chamber of the fuel tank when the fuel tank cap is installed on the fuel tank; and an inner shell at least partially disposed within the cylindrical chamber, the inner shell including an engagement portion that is engageable with the neck and a protrusion engageable with the arm to selectively couple the cap shell and the inner shell for rotation in unison.
 2. The fuel tank cap of claim 1, wherein the cap shell includes a lobe that defines a lobe space, the lobe space disposed near the arm.
 3. The fuel tank cap of claim 2, wherein the arm is substantially disposed outside of the lobe space when the cap shell and inner shell are coupled for rotation and the arm is deflected at least partially into the lobe space to decouple the cap shell and the inner shell.
 4. The fuel tank cap of claim 2, wherein the arm is one of a plurality of arms and the lobe is one of a plurality of lobes, each lobe defining a lobe space and each arm disposed near one of the lobe spaces.
 5. The fuel tank cap of claim 4, wherein each of the plurality of arms is deflectable into the lobe space to decouple the cap shell and the inner shell such that the cap shell is rotatable relative to the inner shell
 6. The fuel tank cap of claim 1, wherein the engagement portion includes threads.
 7. The fuel tank cap of claim 1, wherein the protrusion includes a first side engageable with the arm to couple the cap shell and the inner shell for rotation in unison.
 8. The fuel tank cap of claim 7, wherein the first side is substantially planar.
 9. The fuel tank cap of claim 7, wherein the protrusion includes a second side engageable with the arm to couple the cap shell and the inner shell for rotation in unison when a torque applied to the cap shell is at or below an engaged value.
 10. The fuel tank cap of claim 9, wherein the second side of the protrusion engages and displaces the arm to allow the cap shell to rotate relative to the inner shell when the torque value exceeds the engaged value.
 11. The fuel tank cap of claim 9, wherein the second side is not planar.
 12. The fuel tank cap of claim 1, wherein the cap shell includes one of a bead and a recess that extends around the cylindrical wall, and the inner shell includes the other of the bead and recess, the bead engaged with the recess to rotationally couple the cap shell and the inner shell.
 13. The fuel tank cap of claim 1, wherein the arm is connected to the cover portion such that the arm is supported in a cantilever fashion.
 14. A fuel tank cap engageable with a neck that defines a neck axis, the fuel tank cap comprising: an inner shell rotatable relative to the neck to move between an engaged position and a disengaged position; a cap shell including an arm that defines an arm axis; and a protrusion extending from the inner shell, the protrusion cooperating with the arm to couple the inner shell and the cap shell for rotation in unison from the disengaged position to the engaged position, the protrusion displacing the arm such that the cap shell rotates independent of the inner shell when rotated beyond the engaged position, the protrusion engaged with the arm to couple the inner shell and the cap shell for rotation in unison from the engaged position to the disengaged position.
 15. The fuel tank cap of claim 14, wherein the arm axis is substantially parallel to the neck axis.
 16. The fuel tank cap of claim 14, wherein the inner shell includes a threaded portion and the neck includes a threaded portion, the inner shell threadably engageable with the neck.
 17. The fuel tank cap of claim 14, wherein the cap shell includes a cover portion that is substantially normal to the neck axis and wherein the arm extends in a cantilever fashion from the cover portion.
 18. The fuel tank cap of claim 14, wherein the cap shell includes a lobe defining a lobe space, and wherein a portion of the arm is movable into the lobe space.
 19. The fuel tank cap of claim 18, wherein the arm is one of a plurality of arms, and the lobe is one of a plurality of lobes, each lobe defining a lobe space, at least a portion of each arm movable into one of the lobe spaces.
 20. The fuel tank cap of claim 19, wherein the protrusion is one of a plurality of protrusions and wherein the number of protrusions is substantially equal to the number of arms.
 21. The fuel tank cap of claim 14, wherein the arm Includes a first angled surface and the protrusion includes an angled surface engageable with the first angled surface to couple the cap shell and the inner shell for rotation.
 22. The fuel tank cap of claim 21, wherein the first angled surface and the angled surface are angled such that when engaged, rotation of the cap shell produces a force that biases the arm toward the inner shell.
 23. The fuel tank cap of claim 21, wherein the arm includes a second angled surface and the protrusion includes an arcuate surface engageable with the second angled surface to couple the cap shell and the inner shell for rotation.
 24. The fuel tank cap of claim 23, wherein the second angled surface and the arcuate surface are such that when engaged, rotation of the cap shell produces a force that biases at least a portion of the arm away from the inner shell.
 25. A fuel tank cap engageable with a neck of a fuel tank that defines a neck axis, the fuel tank also having a fuel chamber adapted to contain fuel, the fuel tank cap comprising: a cap shell including a cover portion that is substantially normal to the neck axis and a substantially cylindrical wall extending from the cover portion to at least partially define a substantially cylindrical chamber; an arm extending from the cover portion toward the fuel chamber of the fuel tank; an inner shell at least partially disposed within the cylindrical chamber and engageable with the neck, the inner shell rotatable relative to the neck to move between a disengaged position and an engaged position; and a protrusion having a first side and a second side, the first side engageable with the arm to couple the cap shell and inner shell for rotation from the engaged position to the disengaged position, the second side engageable with the arm to couple the cap shell and inner shell for rotation from the disengaged position to the engaged position when a rotational torque is below an engaged value, the second side operable to displace the arm such that the cap shell rotates independent of the inner shell when the rotational torque exceeds the engaged value.
 26. The fuel tank cap of claim 25, wherein the inner shell includes a threaded portion and the neck includes a threaded portion, the inner shell threadably engageable with the neck.
 27. The fuel tank cap of claim 25, wherein the cap shell includes a lobe defining a lobe space, and wherein a portion of the arm is movable into the lobe space.
 28. The fuel tank cap of claim 27, wherein the arm is one of a plurality of arms, and the lobe is one of a plurality of lobes, each lobe defining a lobe space, at least a portion of each arm movable into one of the lobe spaces.
 29. The fuel tank cap of claim 28, wherein the protrusion is one of a plurality of protrusions, the quantity of protrusions being substantially equal to the quantity of arms.
 30. The fuel tank cap of claim 25, wherein the arm includes a first angled surface and the protrusion includes an angled surface engageable with the first angled surface to couple the cap shell and the inner shell for rotation.
 31. The fuel tank cap of claim 30, wherein the first angled surface and the angled surface are angled such that when engaged, rotation of the cap shell produces a force that biases the arm toward the inner shell.
 32. The fuel tank cap of claim 30, wherein the arm includes a second angled surface and the protrusion includes an arcuate surface engageable with the second angled surface to couple the cap shell and the inner shell for rotation.
 33. The fuel tank cap of claim 32, wherein the second angled surface and the arcuate surface are arranged such that when engaged, rotation of the cap shell produces a force that biases the arm away from the inner shell. 